Cory Monteith, who rose to fame as a jock-turned-geek heartthrob in the Fox hit Glee, died Saturday at the Fairmont Pacific Rim hotel in downtown Vancouver. He was 31.

Monteith voluntarily admitted himself into a rehab facility in March for substance addiction. In late April, the star completed the program and checked out. His last public outing was with his girlfriend and Glee co-star, Lea Michele, June 8 at the Chrysalis Butterfly Ball.

News of the star’s death rocked Hollywood as stars reacted via Twitter:

Ellen DeGeneres: “My heart breaks for the friends and family of Cory Monteith. What a loss.”
Nina Dobrev: “I’m gutted. Shocked and saddened to hear the news, my heart goes out to Cory’s family and friends. Let’s respect their space as they grieve.”
Kim Kardashian: “Just heard about the death of Cory Monteith. So sad. Prayers 4 his family. Praying 4 Lea too! Words can’t describe what they must be feeling.”
Lance Bass: “Devastated about the news of Cory Monteith – such an incredible guy – my thoughts are with his family and friends.”
Katy Perry: “Rest in peace Cory. My heart goes out to his family and loved ones. Our prayers are with you.”
John Stamos: “We talked about how lucky he felt to be alive-and sober. We talked about playing drums. Glad i knew you Cory.”
Demi Lovato: “#RIPCoryMonteith… So unbelievably tragic. Please #prayforLea.”
Neil Patrick Harris: “How sad to read about Cory Monteith passing away. What a shame. He was a lovely, kind, talented guy and will be missed.”
Julianne Hough: “One of the kindest people I’ve ever met! My heart breaks for Cory’s family and loved ones… You will be missed and forever loved Cory!”
Dot-Marie Jones: “I have no words! My heart is broken.”
Josh Sussman: “I am so saddened to hear about Cory. He was such a great guy/Super-kind &warm.”
Harry Shum Jr: “At this time, please send nothing but love and light. This tragic news still doesn’t seem real to me. I love you Cory.”
Zooey Deschanel: “What an absolutely tragic loss of a very talented young man.”
Rihanna: “Cory Monteith, may your spirit be at peace, and may you fly with the angels… Heartbreaking, my prayers are with all of his loved ones!”